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Biomedical subjects

D L Smith

Publications and source records attributed to D L Smith.

At least 271 records · Page 15Linked to original sources
PubMed1991

Elucidation of the primary structures of proteins by mass spectrometry.

A combination of new mass spectrometric methods that can be used to determine the primary structures of proteins, including post-translational modifications, with unprecedented speed and accuracy is described. Structural characterization of alpha-crystallins from bovine lenses has been used to illustrate the methods. The molecular weights of alpha-crystallins fractionated, but not to homogeneity, by reversed-phase HPLC were determined with an uncertainty of 0.01% which is at least 100 times more accurate than is possible using conventional methods. This information was used to identify the primary gene product as well as its phosphorylated and truncated forms. Molecular weight maps of proteolytic digests of these proteins were determined by directly coupled capillary HPLC fast atom bombardment-mass spectrometry. From these maps, the entire amino acid sequence was confirmed, and the phosphorylated peptide was identified. The MS/MS daughter ion mass spectrum of the phosphorylated peptide provided sufficient information to determine which residue was phosphorylated. Because protein structure, including post-translational modifications, is determined on the basis of molecular weight, this method has broad application and will be useful for a variety of diverse and challenging problems in protein structure elucidation.

Amino Acid Sequence↗
PubMed1991

Colonic histoplasmosis in acquired immunodeficiency syndrome. Report of two cases.

Colonic histoplasmosis is a rare entity. There have been four previous reported cases within the population of patients with human immunodeficiency virus (HIV) infection. Because of the increasing incidence of HIV infection within regions where histoplasmosis is endemic, this condition may become more common. Gastrointestinal histoplasmosis has protean clinical manifestations, and symptoms are often nonspecific. Any patient with HIV infection who has unexplained GI symptoms should undergo evaluation for possible histoplasmosis. Aggressive long-term amphotericin B therapy has been effective in HIV patients with histoplasmosis. Resection or diversion of symptomatic colonic strictures caused by histoplasmosis may be necessary in addition to medical therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Transient expression analyses of DNA extending 2.4 kb upstream of the human renin gene.

The influence on homologous and heterologous promoter activity of DNA extending 2.4 kb upstream of the human renin gene (REN) was examined by transient expression assay in JEG-3 cells, using the gene for chloramphenicol acetyl transferase (CAT) as reporter, and cotransfection with pCH110 to control for transfection efficiency. Analyses of constituent subfragments of the region 5' of residue -144, using the herpes simplex virus thymidine kinase (tk) promoter to drive transcription, provided no evidence for negative regulatory influences within the -2400 to -144 DNA. That distal 5'-flanking DNA may have little influence on promoter activity is further supported by a sharp decline in nucleotide homology between human, rat and mouse renin genes further upstream than human residue -604. Constructs containing renin DNA to residue +13, i.e., which retained the REN promoter, all displayed very low CAT activities, consistent with negative cis-acting control within the -149 to +13 region. This finding contrasts with results of similar studies for mouse, in which renin gene control was suggested to be mediated primarily via cell-specific trans-acting activator(s) acting on yet-to-be identified enhancer(s). Mouse renin genes have, however, a common DNA insertion that could have disrupted the negative element in this region, and which might contain enhancer target(s) for trans-acting factor(s). In conclusion, the present study involving JEG-3 cells has demonstrated that distal human renin 5'-flanking DNA has little cis-acting influence on promoter activity, whereas DNA located within 100 base pairs of the renin promoter may have a negative regulatory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning, Molecular↗
PubMed1991

Cytotoxic clerodane diterpenes from Polyalthia longifolia.

Bioassay-directed chemical investigation of the stem bark of Polyalthia longifolia Thw. (Annonaceae) has led to a novel clerodane diterpene, 16-oxo-cleroda-3, 13(14)Z-dien-15-oic acid, which was named polyalthialdoic acid (3). The bioassays also led to the previously known related diterpenes, kolavenic acid (2) which has not been reported as a constituent of this plant, and 16 alpha-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1) which is previously known to be in this plant. These structures were identified by chemical and spectroscopic methods. All three compounds (1-3) were significantly bioactive in the brine shrimp bioassay; they strongly inhibited the growth of crown gall tumors on potato discs; and they were cytotoxic in three human tumor cell lines. These activities suggest potential antitumor applications. Compound 3 was the most active (ED50 values ca. 6 x 10(-1) micrograms/ml in the human tumor cell culture systems).

Antineoplastic Agents, Phytogenic↗
PubMed1991

Use of third-generation cephalosporins. Enterobacteriaceae.

Enterobacteriaceae are ubiquitous pathogens that cause community-acquired and nosocomial infections at many sites. Third-generation cephalosporins and monobactams are generally the parenteral drugs of choice for the non-beta-lactamase-producing Enterobacteriaceae, with ceftriaxone usually preferred because it is equally effective to the others and can be given once a day. They are also good alternative drugs for patients with Salmonella infections who fail to respond to or cannot tolerate ampicillin or trimethoprim-sulfamethoxazole.

Animals↗
PubMed1991

Growth and maintenance of an embryogenic cell culture of daylily (Hemerocallis) on hormone-free medium.

Callus cultures of the diploid daylily (Hemerocallis) clone Autumn Blaze' were initiated and maintained in hormone-containing nutrient medium. At various times (from 6 weeks to 1 year) after being initiated, hormone-derived cultures were evaluated for their ability to be maintained and to multiply on hormone-free medium at low pH (between pH 4 and 4.5). Cultures had to be exposed to hormone-containing medium for at least 12 weeks before they could be maintained on hormone-free medium at low pH. The transition to maintainability on low pH hormone-free medium included the production of many aberrant embryonal forms ( neomorphs'). However, all hormone-derived cultures tested consisted entirely of preglobular stage proembryos (PGSPs) after 12-24 weeks on low pH hormone-free medium. PGSP cultures have been maintained and multiplied as such for over 1 year on low pH hormone-free medium. PGSPs continue their development into various somatic embryo stages when cultured on hormone-free medium buffered at pH 5.8. The production of well-formed somatic embryos was greatly enhanced when PGSPs were plated on activated charcoal impregnated filter papers that were placed on top of the agar surface. The gross morphology and histology of the PGSPs and stages of somatic embryo development are presented. The work shows that the ability of hormone-free medium at low pH to permit PGSP multiplication without development into later stages of embryo development is not restricted to carrot.

Cells, Cultured↗
PubMed1991

Betaines of alfalfa : characterization by fast atom bombardment and desorption chemical ionization mass spectrometry.

Leaf tissue of alfalfa (Medicago sativa L.) was found to contain prolinebetaine, pipecolatebetaine, hydroxyprolinebetaine, and glycinebetaine. As n-butyl esters, these chemical species exhibit molecular cations at mass/charge ratio (m/z) 200, 214, 216, and 174, respectively, when analyzed by fast atom bombardment mass spectrometry. The underivatized betaines exhibit protonated molecular ions at m/z 144, 158, 160, and 118, respectively, when analyzed by desorption chemical ionization mass spectrometry. Extensive (>45-fold) genotypic variation for hydroxyprolinebetaine level was identified in alfalfa. Because a significant inverse correlation between prolinebetaine and hydroxyprolinebetaine levels was observed among 15 alfalfa genotypes evaluated, it is possible that these compounds may be derived from a common intermediate. Birdsfoot trefoil (Lotus corniculatus L.) contained prolinebetaine, but only traces of glycinebetaine, pipecolatebetaine, and hydroxyprolinebetaine. Red clover (Trifolium pratense L.) lacked prolinebetaine, pipecolatebetaine, and hydroxyprolinebetaine, but contained appreciable levels of both glycinebetaine and trigonelline. Trigonelline was not detectable in the leaf tissue of any alfalfa genotype or cultivar evaluated.

Journal Article↗
PubMed1991

Renin gene expression in various tissues determined by single-step polymerase chain reaction.

1. Renin mRNA is present in the kidney and, in lower concentrations, in many extrarenal tissues and serves as an index of renin gene activity, as well as potential renin or prorenin synthesis in cell populations within those tissues. Unfortunately the quantity can be very low. 2. A new, highly sensitive technique is described for detection of renin mRNA that involves the enzyme Taq polymerase for both reverse transcription of renin mRNA into renin cDNA and for amplification of the 769-1099 nucleotide segment by the polymerase chain reaction (PCR), all of which involves a single reaction mixture. 3. In this way renin mRNA was detected in kidney and several extrarenal tissues as a PCR product of approximately 330 base pairs on agarose gels by ethidium-bromide staining or hybridization probing. The region of renin mRNA chosen for amplification spanned several intron sites in the coding sequence so that the presence of amplicants derived from genomic DNA could be readily discriminated, as a band of approximately 1.5 kilobases. 4. Thus single-step PCR offers a powerful new approach to detection of renin mRNA.

Animals↗
PubMed1991

The posttranslational processing of beta-endorphin in human hypothalamus.

beta-Endorphin is posttranslationally processed to six derivatives, which, although structurally similar, produce distinctly different biological effects. beta-Endorphin 1-31 is a potent opioid receptor agonist, but beta-endorphin 1-27 exhibits antagonist properties, and beta-endorphin 1-26 and the alpha-N-acetyl derivatives of all three peptides lack opioid receptor activity. In the present study, we identified the beta-endorphin peptides synthesized in human hypothalamus using cation exchange HPLC. First, we tested whether postmortem changes occur by storing rat hypothalami at 4 degrees C. This demonstrated that relative amounts of the six beta-endorphin forms did not change for up to 24 h, although total beta-endorphin immunoreactivity significantly declined after 6 h. HPLC analysis of human hypothalami revealed that beta-endorphin 1-31 was the principal form, constituting 58.4 +/- 5.4% of total immunoreactivity. Substantial amounts of beta-endorphin 1-27 (13.4 +/- 1.2%) and beta-endorphin 1-26 (13.1 +/- 1.6%) were also present, but alpha-N-acetylated forms were quantitatively minor, each comprising approximately 5% of total beta-endorphin. A similar processing pattern occurred in preoptic and suprachiasmatic areas of the hypothalamus. These results show that, despite differences in primary sequence, beta-endorphin is processed similarly in both rat and human hypothalamus. Opiate-active beta-endorphin 1-31 is the principal form in both species.

Adult↗
PubMed1991

Prorenin and gene activation.

After the discovery of an inactive, putative renin precursor that could be proteolytically activated, and the proteases involved in vivo, Morris and co-workers directly demonstrated that renin is indeed synthesized as a "pro" form, and from genetic coding sequences they provided the structure of human prorenin. The gene is inactive and must be activated in prorenin-synthesizing tissues. To study the mechanism involved, we have performed transient expression analyses of putative regulatory DNA of the human gene (REN). 5'-Flanking DNA, extending from residue -144 to -2400, was linked to a reporter gene, viz. that for chloramphenicol acetyl transferase (CAT), and its ability to drive a heterologous (thymidine kinase, tk) promoter was examined by transfecting plasmid constructs into cells in culture and measuring CAT activity 48 h later. Because suitable renin-synthesizing cells were not available, choriocarcinoma (JEG-3) and cervical carcinoma (HeLa) cells were used. Although this DNA caused a reduction in CAT activity relative to the positive control, examination of a range of subfragments suggested that the -2400 to -144 region did not contain negative regulatory elements. In contrast, all fragments containing the -149 to +13 DNA segment gave CAT activities that were lower than the promoterless control. Together, the data were consistent with the presence of negative regulatory element(s) in that fragment of DNA that contained the REN promoter.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloramphenicol O-Acetyltransferase↗
PubMed1991

The chest X ray in Q-fever: a report on 69 cases from the 1989 West Midlands outbreak.

Acute and serial chest radiographic appearances of Q-fever in a large UK outbreak in the West Midlands are described. In 69 acute films (taken within 20 days of onset of illness), 10% of films were normal. Appearances in 62 abnormal films were varied and, in contrast to some previous reports, showed no features that might distinguish Q-fever pneumonia from pneumonias of other origins. Analysis of serial films in 47 cases showed that complete radiographic resolution frequently took up to 6 months, longer than has been described previously. Initial appearances deteriorated over the first 2 weeks of radiographic surveillance in 20% of cases. No relationship was found between the extent of radiographic change and the age of the patient or the presence or absence of respiratory symptoms. Age did not affect time to resolution.

Adult↗
PubMed1991

"Tumoral" enthesopathy: a juxtacortical osteosarcoma simulation.

A patient with psoriatic arthritis involving the ankles and feet developed a rapidly progressive large juxtacortical bony proliferative lesion arising from the right proximal radius at the bicipital tendon insertion site. The radiographic pattern was compatible with a juxtacortical periosteal osteosarcoma. We discuss the similar radiographic findings between a surface osteosarcoma and florid inflammatory enthesopathy that was found upon biopsy.

Adult↗
PubMed1991

The effect of glaucoma filtering surgery on corneal endothelial cell density.

Corneal endothelial cell counts were obtained preoperatively and 3 months postoperatively in 46 eyes undergoing glaucoma filtering surgery. Average central endothelial cell loss in eyes without postoperative iridocorneal touch was 1.6%. In eyes with iridocorneal touch (Spaeth's grades 1 and 2), the average cell counts decreased by 7.1% and 9.3%, respectively. The average loss for combined grades 1 and 2 (8.1%) approached statistical significance (P +/- .06). The average loss in two patients with corneolenticular touch (Spaeth's grade 3) was greater than 50%. These findings suggest that early postoperative iridocorneal touch is unlikely to lead to corneal compromise in most eyes, but that corneolenticular touch can result in severe endothelial cell loss.

Aged↗
PubMed1991

The effects of glaucoma medications on Tenon's capsule and conjunctiva in the rabbit.

Glaucoma filtering surgery fails most frequently due to fibrosis at the episcleral-conjunctival/Tenon's capsule interface. Sherwood et al have suggested that chronic topical antiglaucoma medications increase conjunctival inflammatory cells, which could increase the likelihood of fibrosis and subsequent bleb failure. In a pilot study in a rabbit model, we placed timolol, pilocarpine, and epinephrine, or a combination of all three, in one eye of 24 animals twice daily for 7 months. The fellow eye received distilled water. Microscopic examination revealed no statistically significant change in the number of acute or chronic inflammatory cells, fibroblasts, or goblet cells in the treated as compared with the control eyes. A longer duration of drug administration, or drug administration followed by surgical intervention, may be required to produce an effect on the conjunctiva and Tenon's capsule, if such an effect exists.

Administration, Topical↗